Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$216.29	9.808%	$237.5037	$237.50	$237.50	$237.50
Purchase #2	$35.29	4.590%	$36.9098	$36.91	$36.90	$36.90
Purchase #3	$192.56	8.333%	$208.606	$208.61	$208.60	$208.60
Purchase #4	$63.34	12.728%	$71.4019	$71.40	$71.40	$71.40
Purchase #5	$171.25	10.209%	$188.7329	$188.73	$188.75	$188.70
Purchase #6	$234.70	6.475%	$249.8968	$249.90	$249.90	$249.90
Purchase #7	$130.38	3.369%	$134.7725	$134.77	$134.75	$134.80
7 purchase totals =	$1,043.81		$1,127.8236	$1,127.82	$1,127.80	$1,127.80